The present invention is directed to a novel self-leveling wheelbarrow. The wheelbarrow incorporates self-adjusting legs which conform to the terrain and lock into place when at rest on the ground. The self-leveling feature offers added stability and provides a significant advantage over conventional wheelbarrows when used on sloping or uneven terrain. Several different designs for locking the legs are described herein.
Conventional wheelbarrows are well suited for use on smooth, level surfaces. Their ease of use, excellent mobility, and low cost have made them the material handling equipment of choice for moving small loads in the construction and landscaping industries. As a result of the great success of the conventional wheelbarrow, their basic design has remained essentially unchanged for many years. However, due to its high center of gravity, fixed leg assembly, and the inherent instability of a tripod-style base, the use of a conventional wheelbarrow on uneven or sloped terrain is somewhat restricted. These factors result in a tendency to overturn if the legs are not resting on a level surface. When level ground cannot be found in close proximity to the working area, the worker may be forced to park the wheelbarrow some distance away. The additional walking between the wheelbarrow and the working area during loading or unloading reduces worker productivity. When parked on uneven or sloping terrain, extra care must be taken to avoid overturning and potential injury to the user. As shown in FIG. 1, often a wedge or block X is placed beneath one leg L of the wheelbarrow W in order to provide additional stability and prevent overturning.
The present invention is directed to an improved wheelbarrow that is stable on sloping or uneven ground, the wheelbarrow having features that eliminate its tendency to overturn. Aspects of the present invention incorporate self-adjusting mechanisms added to the leg assembly which consequently allow the legs to conform to the terrain as the wheelbarrow is lowered and locked into position when both legs are in contact with the resting surface. The self-leveling action increases stability and maintains the wheelbarrow, in particular the basin, in a level position. The center of gravity remains very nearly centered above the midpoint of the legs, thus the weight is more evenly distributed between the legs, and the tendency to overturn is diminished.
In certain aspects, the present invention comprises a self-leveling wheelbarrow having a basin, a wheel disposed beneath the basin near the basin's front end, and a handle assembly secured to the basin. The wheelbarrow further includes a rear mounting bracket secured near the rear end of the basin, the mounting bracket having a top end secured beneath the basin, mounting bracket further having a vertical slot communicating therethrough. The leg assembly of the wheelbarrow includes a pair of legs secured to one another by a centrally disposed plate, such that the one leg is positioned beneath the right side of the basin and the other leg is positioned beneath the left side of the basin. The centrally disposed plate includes a top edge. A pin extends from the plate and is slidably engaged within the slot to allow the leg assembly to move vertically within the slot and to rotate in a clockwise and counterclockwise direction about the pin. The wheelbarrow further includes a locking assembly secured beneath the basin in vertical alignment with the top edge of the leg assembly plate. The locking assembly is configured to engage the top edge of the leg assembly plate when the legs are in contact with underlying terrain. In one embodiment, the locking assembly further includes a first pair of opposing cam devices, each of the cam devices having an eccentrically fixed pivot end about which the cam device may rotate, and a free end having an outer edge, each of the cam devices spaced a distance apart to create a channel between the outer edges. This channel extends in horizontal alignment with the top edge of the leg assembly plate and is configured to engage the top edge therein. In operation, as the legs of the leg assembly contact the underlying ground as the wheelbarrow is parked upon the terrain, the leg assembly rotates about the pin within the slot to accommodate the contour angle of the terrain, sliding the top edge of the plate within the locking assembly channel in friction-fit contact with the outer edges of the opposing cam devices. This action consequently locks the plate therebetween to prevent the leg assembly from rotating further about the pin the direction of travel (i.e. either in a clockwise or a counterclockwise direction of travel). In addition, the locking assembly may include a second pair of cam devices positioned adjacent to the first pair of cam devices to prevent rotation in both the clockwise and counterclockwise directions simultaneously.
Other aspects of the inventive wheelbarrow include different locking assemblies, including one or two locking bars secured beneath the basin and aligned above the top edge of the leg assembly plate when the leg assembly is in contact with the ground surface. The locking bar(s) has an eccentrically fixed pivot end about which the bar may rotate and a free end having a horizontal slot in alignment with the top edge of the leg assembly plate and configured to engage the top edge of the plate therein. As the leg assembly contacts the underlying ground and the leg assembly rotates about the pin to accommodate the contour of the ground, the top edge of the plate slides within the slot in friction-fit contact therein, thereby locking the plate therein to prevent the leg assembly from rotating further about the pin in either a clockwise or counterclockwise direction of travel.
Another embodiment of the locking assembly includes a disk brake locking assembly having a pair of disk brake pads aligned on each side of the leg assembly plate, such that upon activation of the locking assembly by a brake lever, the pads squeeze toward one another to engage the plate therebetween.
Other features of the inventive wheelbarrow include the pin extending from the mounting bracket instead of the leg assembly plate, with the vertical slot communicating through the leg assembly plate, as opposed to the mounting bracket.
Moreover, the leg assembly may include, in a series, a rear vertical member to which the rear plate is secured, a horizontal portion integral with the vertical member and adapted to contact the ground, and a front member integral with the horizontal member and terminating into a front plate, the front plate in alignment with a front mounting bracket and secured beneath the wheelbarrow in registration with the rear mounting bracket. In this embodiment, the pin comprises an elongated rod extending from the front mounting bracket, front leg assembly plate, through the vertical slot in the rear leg assembly plate, and secured to the rear mounting bracket. Alternatively, the vertical slot may be located in the rear mounting bracket.